Method for preventing build-up of light gases in a paraffin isomerization process



Patentes Dec. so, 1947 UNITED STAT E S OFFHCE METHOD FOR PREVENTINGBUILD-UP 01.*"- LIGHT GASESl IN A PARAFFEN ISOMERIZA- TION PROCESS`loseph` K. Roberts, Flossmoor, ll., assignor to Standard Oil Company,Chicago, Ill., a corporation of Indiana This invention relates to animproved process and apparatus for the isomerization of light par-Vainic hydrocarbons by means of an aluminuml halide-hydrocarbon complexactivatedI by hydroa gen halide and under considerable hydrogen pres--vactivator in areaction activated by a hydrogen halide. A further objectis to provide improved methods andmeans for recovering and reintroducingactivators in an isomerization process. A-

further' object is to provide improved means for venting lighthydrocarbon gases from a continuous aluminum chloride isomerizationsystem Without appreciable losses' of hydrogen chloride. Other ob'jectsand' advantages will become apparent as the detailedv description of. myinventionI proceeds.

When my invention isapp'lied to relinery'naphthas I rst fractionate thenaphthas to remove undesirable components; for the isomerization of acharging stock consisting essentially'cf Cfr-C6A hydrocarbons, forinstance, it is desirable to remove substantially allof the heptanes andto'have" relatively lowA concentrations of aromatics and naphthenes.charging stock is employed' for absorbing hydrogenchloride from gasesproduced' in the system, and this is an important' feature of myprocess. Another part of the charging stock maybe employed for making'upaslurry of fresh aluminum chloride, although recycled products mayserve` this purpose. The part' of the charge-containing hydrogenchloride is passed through' a heat exchanger and' is then introduced'into a reactor. Make-up aluminum chloride and hydrogen are also added tothe reactor.

'I'he reactor is operated Lat a' temperature Within the'approximaterange of 100. to 460 F'.preferf ably 200'to300" Ek, aty a pressurewithin the ap proximate rangeof 100 to 3G00 pounds per'square inch,preferably 500 to l'pounds per square' inch. For Cir-Cs hydrocarbons Ihave found that excellentresult's are obtainable at atemperaturewithinthe approximate vicinity of 250 F. and a pressureWithin the approximate vicinity of about. 850 to SOO lpounds persquaresinch.

Thev amount' of hydrogen required will vary somewhat with temperature,pressure and hydro. genchloride'concentration inzthe reaction zone,rangingafrom' about 20fcubicrfeet per barrel of.

At least' a: substantial part of the stock charged at low temperatures,low pressures and low hydrogen chloride. concentrations to 200 or morecubic feet per barrel at high temperature, pressures and hydrogenAchloride concentrations. For optimum conditions of operation on Cs-Cshydrocarbons the actual hydrogen consumption Will be about cubic feetper barrel and in order to insure the presence of the requisite anountof hydrogen inthe reactor I prefer to introduce about 100 to about 300,preferably about 200 cubic feet of hydrogenper. barrel. ofr charging.stock.

The amount of make-up aluminum chloride. may be Within the approximaterange ofY .l to pounds per barrel of total charging` stock, usuallywithin the approximate range of 1 to 2 pounds per barrel. The amount ofhydrogen chloride may be within the approximaterange of 5 to 30 poundsof hydrogen chloride per barrel of. total stock0 charge-d, usuallyWithin the general vicinity of 8 or 10 pounds per barrel but onlyV asmall portion of the hydrogen chloride is'actuall'y consumed so that themajor portion of it will be recovered and reintroduced as will behereinafter described.

While the materials-introduced into the reactor with the charging stockare aluminum chloride, hydrogen chloride and hydrogen, the effectivecatalyst in the reactor is an aluminum chloridehydrocarbon complex whichmay contain more or less dissolved or uncombined aluminum chloride. Atthe beginning of an operation I prefer to have the reaction towers atleast about half full of said complex althoughsaid complex may be formedin situ by the combination ofv hydrocarbons withY aluminum chlorideinthe presence of hydrogen. chloride. The fresh complex is relatively.nonviscous and has a specic gravity about twice as great as that of thecharging stock so that when charging stock is introduced at the base ofthe reactor it flows asa dispersedphase' upwardly through saidcomplexthus effecting intimate contact between the charging stockand thecomplex. The incoming charging stock is mainly in the liquid phase butit may be' partially vaporized. by the gaseous hydrogen, about half ofthe' vol'-` ume of the upflowing stream being gaseous be#- cause of theintroduced hydrogen which serves the function of promoting turbulenceand effecting intimate mixing of charging stock and com plex. Based on.stock' charged and the total amount of complex in the reactor the spacevelocity should be within the approximate range of .2 to 'i volumes ofliquidfeedper hour per volume of complex inthe reactor, preferablyabout` 1/ato 2 volumes of feed per hour per volume of complex.

I In the upper part of the reactor suicient settling space is providedfor permitting separation of complex from the clear reaction products.To insure adequate settling I either increase the cross-sectional areaof the upper part of the reactor or provide a separate chamber of largehorizontal cross-sectional area. The clear products are then passedthrough a cooler to a 10W pressure settling chamber for the release ofhydrogen chloride and dissolved catalyst.

By separating the catalyst at reduced temperature and pressure thecatalyst can be returned directly to the reactor as a complex or slurry.The gases containing hydrogen chloride are recycled and scrubbed by aportion of the charging stock for recovering the hydrogen chloride. Thesubstantially catalyst-free products may be charged to a hydrogenchloride stripper and thence to a fractionation system.

I have found that a considerable amount of hydrogen chloride may berecovered from the products in a simple stripping column which isoperated at a pressure of about 200 pounds per square inch, a toptemperaturein the approximate range of 100 to 150 Rand a bottomtemperature in the approximate range of 300 to 400 F. This stripper maybe operated under such conditions as to take substantially all of thehydrogen chloride overhead while removing with the liquid anycondensibles that might otherwise tend to build up in the system. Thefinal products therefrom are neutralized with caustic, water washed andfractionated or stabilized.

I may employ a, multi-stage reaction system, the first stage being withrelatively spent complex at relatively high temperature and the secondstep with relatively fresh complex at a lower temperature. Complex fromthe low temperature stage may be transferred to the high temperaturestage. Substantially constant complex activity may be maintained in eachzone by the addition of active materials thereto and the withdrawal ofrelatively spent catalyst therefrom. Hydrogen chloride may be recoveredfrom the spent catalyst by treatment with water or sulfuric acid.

The invention will be more fully understood from the following detaileddescription of a specic example thereof read in connection with theaccompanying drawing which forms a part of this specification and whichis a diagrammatic ow sheet of my improved process as applied to a 5000barrel per day isomerization plant for Cs-Cc hydrocarbons.

About 5000 barrels per day of light naphtha is charged by pump I throughheat lexchanger l I to an intermediate point of light napthafractionator l2. This fractionator is provided with conventional heatingmeans i3 at its base and is operated under such conditions that pentanesand hexanes are taken overhead while heptanes and heavier hydrocarbonsare Withdrawn from the base of the column through line I4. The hexanes,pentanes and any butanes that may be present are taken overhead throughline i5 and cooler I6 to reflux drum l1, A portion of the refluxcondensate is returned by pump I8 through line i9 to the top of thefractionator to serve as reflux. When substantially butano-free chargingstock is desired the rest of the reflux condensate may be withdrawn fromthe system through line 20 and 20a. In this case the pentanes andhexanes are withdrawn. aS L Separate fraction (diagrammaticallyillustrated as a side stream) by pump 2l through cooler 22, about ormore of this stream being introduced through line 23 to the top ofabsorber 24 and the rest of the stream (or a pretreated or recycledstream) being introduced through line 25 to aluminum chloride slurrytank 2B. I may, however, leave any butanes in the charging stock so thatthe side stream draw-off is unnecessary. For example, about 900 barrelsper day or'more of reflux condensate may be introduced through lines 2'?and 23 to the top of the absorber and about barrels per day or less ofthe reflux condensate may be introduced through line 2B and line 25 toslurry tank 26.

The hydrogen chloride required for the reaction is absorbed in at leastthe major portion of the feed stock before it is introduced into thereactor. The hydrogen chloride absorber may be about 11/2 feet indiameter by 28 feet high and it may operate at a pressure of about 100to 300, for example about 200 to 250 pounds per square inch. A stream ofhydrogen chloride gases from the system is introduced at the base ofthis absorber through line 29. Make-up hydrogen chloride may beintroduced through line 30. Instead of make-up hydrogen chloride I mayemploy chlorine, an alkyl chloride or other substance which will supplythe necessary hydrogen halide activator under reaction conditions. Iprefer, however, to employ hydrogen chloride and to generate it ifnecessary in a separate generator.

The hydrogen chloride generator 3l may be of any known type. Thechlorine supplying agent introduced through line 32 is preferablychlorine gas although it may be sodium chloride, 22 muriatic(hydrochloric) acid or other halogen containing reagent. The hydrogensupplying agent introduced through line 33 may be hydrogen gas, ahydrocarbon, sulfuric acid, etc. Thus hydrogen and chlorine may beburned in generator 3l to supply hydrogen chloride. Wax tailings orother hydrocarbons may be introduced through line 33 and chlorinated bychlorine gas introduced by line 32 to produce hydrogen chloride andchlorinated hydrocarbons (additional hydrogen chloride may of course beobtained from the latter). Sodium chloride or hydrochloric acid may beintroduced through line 32 and sulfuric acid through line 33 but in mysystem this hydrogen chloride generator operates under such pressurethat no compressors are required for introducing the hydrogen chloridethrough line 34 to the base of absorber 24 and this hydrogen chloridedoes not require the puriflcation which is generally necessary even forthe production of commercial grades of hydrochloric acid. By-productsfrom the hydrogen chloride generator are withdrawn through line 35.

The hydrogen chloride picked up in absorber 24 should be suicient togive an amount of hydrogen chloride in the stock entering the reactorswithin the approximate range of 2% to 10%, i. e., in the generalvicinity of 5% by Weight based on stock charged. Most of this hydrogenchloride may be obtained by gases from line 29. Unabsorbed gases such assmall amounts of hydrogen, methane, etc. are purged from the systemthrough line 36, thus eliminating not only gaseous impurities from line29 but also gaseous impurities from line 34.

The hydrogen chloride-rich charging stock .from the base of absorber 24is pumped by pump .3.1 through .heater 38', :through llines 3 0 and 40tothe [base of rstreactorrlll at :a pressure within the approximater range.of `50.0 to 1500 pounds per square inch, for example about 850 or A900pounds'per square inch. Hydrogen from source 42 (or from other sourcesthat will ber hereinafter described) is introduced by compress-or :i3and line 44 into line 39 in amounts within the approximate range of 1,00to 3.00, for example about 200 cubic feet per barrel of stock charged tothe reactor (the hydrogen being measured at 60 F. and atmosphericpressure). Aluminum chloride :from source 45 is introduced throughsuitable feeding means i6 :into slurry tank 26 at such a rate thatY theamount of aluminum chloride in the slurry `is about one or two poundsper gallon. Based on total charging stock introduced into the reactor,the amount of aluminum chloride introduced through line 30 by pump Q1and line 48 is within the approximate range of .1 to i pounds,preferably about 1 or 2 pounds per barrel of charging stock. 'The streamentering` reactor il through line 40 may be at a temperature Within theapproximate range of 200 F. to 300 F., for example about 250 F.Preferably the make-up aluminum chloride is introduced in a. separatestream through line lavto avoid line plugging Vat or near the pointwhere the slurry meetsv the hydrogen chloride-charging' stock stream.

Reactor 4I may be a vertical tower. When the reaction is initiated thisreactor may be about half lled with an aluminum chloridehydrogenchloride-hydrocarbon complex, the

density ofv which is Within the approximate range of' 1.2 to 1.7 butwhich may be maintained during the reaction Within the general vicinityof 1.5 by methods Vhereinafter described. The density of the liquidhydrocarbon charging stock is less than half that of the complex. Thecharging stock is chiefly in the liquid phase but some of it will beVaporized by the upflowing gases which constitutei about one-half thevolume of the upflowing stream and which produce turbulence and intimatemixing in the reaction tower. The space velocity should generally beWithin the approximate range of .2 to 4 volumes of liquid charging stockper hour per volume of complex in the reactor or reactors and underpreferred operating conditions with a single reactor it should be withinthe general vicinity of one volume of liouid charging stock` per hourper volume of catalyst complex inthe reactor. Higher space velocitieswill. of course, be employed in an individual reactor. When a pluralityof reactors are employed in` series.

Catalyst complex. settles from the upflowing reaction products in thetop of the tower and if desired the tower top. may be enlarged toprovide increased settling area. I prefer, however, to withdraw the`reaction products from thev tower top through lines i9 and 50 to asoakingv drum or Warm settling chamber 5! which Vmay be a horizontal orslightly inclined drum. I have discovered that there isv a large amountof dissolved catalyst in the products at this point and this dissolvedcatalyst in a soaking zone may haveabenecial eect on productdistribution. 'In other words, the isomerization equilibrium in drum 5|is not the same as in reactor lil and this 'supplemental contact withdissolved catal'yst in drum 5l may contribute to additional formation ofdesired isomerization products. The complex carried into the soakingzone is often-,as hiicliasv freshly @prepared complex; il'. e. it may'be.quite .different in its properties than the;.average `complexin theinitial reactor.

Drumgl. also serves the important function oflremoving anyiundissolvedcomplex, the separated complex being withdrawn from the base of 'thedrum, through line 52 and returned without necessity of pumping; Complexremoval at this point helps to prevent, fouling of the heat exchangerWhen` clear products are withdrawn through. line'53, through cooler(heat exchanger) 54 and pressure reduction valve 55 to the cool settlingdrum 56 which is maintained ata temperature .of about F. or less and ata pressure Within the approximaterange of 100 to 300, for example.about. 200 to Y250 pounds per square inch. .'Ihe..cool.se.ttler may be ahorizontal or slightly inclined drum. Released gases leave the top ofthe cool Vsettler 5B through line 51 which discharges into line 29. Thereduced pressure and cooling elects a considerable precipitation ofcatalyst material .in the cool settler and the precipitated` catalystmaterial is withdrawn as a slurry from the base of this settler by.means of pump 58 in line 59. i

The clear product which is now. substantially free from catalyst andwhich contains only a small amount of hydrogen chloride is Withdrawnthrough line 60 and introduced by pump 0I into hydrogen chloridestripping tower 62 which may be a column about 3 feet in diameter andabout 33 feet in height. This stripping column may be provided Vwithheating means 63 at its base and it may be operated ata pressure ofabout 200 to 25.0 pounds per square inch with a top temperature withinthe approximate Arange of 100 to 150 F. and a bottom temperature withinthe approximate range of 300 to 400 F. The removed hydrogen chloridetogether with released gases such as hydrogen, methane, etc. is takenoverhead through line B4 to line 20.v Condensibles that might otherwisebuild up in the system are removed with the liquids from the base of thestripper.

The liquid from the base 0f the stripper' is introduced at `a loW pointin scrubbing tower 65 either directly through line 65 or through acooler 61. Scrubber 65 may be a tower provided with suitable baflies,trays or bubble plates for effecting intimate contact of the upowingproducts with a concentrated caustic solution introduced through line63. The upiiowing neutralized products are washed free from caustic inthe upper part of the tower by water introduced through line 69. Spentcaustic solution is withdrawn from the base of the scrubber through line10. The wash Water may be withdrawn from a traoout plate above the pointof caustic inlet if desired.

The water washed' product may be withdrawn as such through line |28yor'it may pass from the top of scrubber -'through line 'll and heat'exchanger' 'l2 to an intermediate point in stabilizer '53. Thisstabilizer is provided with conventional heatingmeans 14 atitsA base.Butanes and any lighter products may be taken overhead through line 'I5through cooler-condenser 7S to redux drum 1T from which gases may bevented throughl'ine '18. Condensed reflux may be-returned'by pump l0through line 80 to the top of stabilizer 13. A stream consisting of amix'- ture of normal and isobutanes maybe withdrawn from the systemthroughv line 8l.

If desired a singley isomate fraction may be withdrawn from the base of`the stabilizer 7, through heat exchanger 'I2 and line 82. We may,however, withdraw only the heaviest isomate at this point and we maywithdraw a light isomate as a separate fraction (diagrammatically shownas a side stream) through line 83. The isomate may be fractionated toinsure the removal of any heptanes or heavier products which may beformed and to obtain a product of desired Reid vapor pressure forblending in desired amounts with isooctane to make a super aviationfuel. A representative analysis of isomate produced in this system maybe approximately as follows:

Per cent by volume Isobutane 2 Isopentane 31 n-Pentane Cyclopentane 3Z-methyl pentane 18 S-methyl pentane 8 2-2-dimethyl butane 202-3-dimethyl butane 2 n-Hexane and heavier 11 If neohexane is a desiredend product it may be separately fractionated and the other iso hexanesmay be recycled for the production of further amounts of neohexane.

4Returning to the reaction system, I may employ a second reactor 84.Products from the rst reactor instead of going to the Warm settlerthrough line 59 may pass through line 85 and heat exchanger 86 into thebase of this second reactor 84. The operating conditions in'the combinedreactors may be substantially the same as in the single reactoroperation although I prefer to operate the second reactor at a lowertemperature than the first reactor. Thus with the first reactor at 300F. or more the second reactor may be at about 250 F. Products from thetop of the second reactor pass through line 81 to the soaking drum orwarm settler 5| as hereinabove described.

Instead of operating the reactors in series they may be operated inparallel by passing only a part of the charging stock through line 46 tothe iirst reactor and by passing the remainder of the charging stockthrough line 88 to the base of the second reactor. By means of thisarrangement one reactor may be ori-stream while another reactor isstanding by for repair or replacement of catalyst complex.

In general the complex becomes more viscous with age and up to a certainpoint the catalyst becomes moreactive with this increasing viscosn ity.These characteristics are apparently determined to a certain extent bythe hydrocarbon content of the complex. Fresh complex may contain up toabout 37% hydrocarbon but when complex is made in situ in the presenceof a large amount of aluminum chloride and after catalyst has been usedfor a period of time .it may contain only or 15% hydrocarbons, thebalance consisting chiey of aluminum chloride. The catalytic activity ofthe complex may be maintained substantially constant by withdrawing aportion of the catalyst from the base of the reactors at about the samerate as an additional amount of aluminum chloride is added theretoeither in the form of relatively fresh complex or in the form of analuminum chloride slurry. Thus catalyst from the second reactor may bewithdrawn through line 89 by means of pump 90 and either introducedthrough lines 9| and 92 to `the first reactor, withdrawn from the systemthrough line 93, or introduced through line 94 to hydrogen chloriderecovery drum 95. Catalyst from the base of the first reactor may bewithdrawn through line 96 by means of pump 97 and introduced throughline 98 to the second reactor, Withdrawn from the system through line 99or passed to the hydrogen chloride recovery drum through line |00. Ifthe second reactor Operates at a lower temperature than the rst reactorwhen in series therewith, I prefer to introduce catalyst from the secondreactor through lines 9| and 92 to the first reactor and to removecatalyst through line |00 from the first reactor to the hydrogenchloride recovery drum 95. For such operation I prefer to introduce apart or all of the make-up aluminum chloride slurry from line 48 to thesecond reactor through bypass line |0| or lla.

Settled catalyst complex from the soaking drum or warm settler 5| may bepassed from line 52 through line |02 to slurry tank 26, or through lines|03 and 98 to second reactor 64' or through lines |04 and 92 to firstreactor 9|. Catalyst slurry from cool settler 56 may be passed from line59 through lines |05 and |02 to slurry tank 26, or through lines |06 and98 to second reactor 84 or through lines |01, |64 and 92 to firstreactor 4|. The liquid from the base of these settlers, particularlyfrom the base of cool settler 56, may be a desirable medium for makingup the aluminum chloride slurry in tank 26. A1- ternatively I may returnrecycled isomerization products, chiefly methyl pentanes, from line 82through lines |08 and |02 for making up the aluminum chloride -slurry intank 26. Instead of recycling isomerized products for making up thealuminum chloride slurry I may pre-treat with aluminum chloride thatportion of the charging stock with which the slurry is to be'made upsince a slurry made with such pre-treated charging stock is more stablethan a slurry made with untreated charging stock,

Spent sludge may be discarded from the system but I prefer to introduceit into drum and to add to the sludge in this drum through line |09 asuflicient amount of sulfuric acid or water to effect recovery ofanhydrous hydrogen chloride. The recovered hydrogen chloride is passedthrough line ||0 to line 29 and absorber 24. The sulfuric acid sludge orcokey residue is withdrawn from drum 95 through line If water isemployed it should be used in less than stoichiometric amounts in orderthat the recovered hydrogen chloride may be substantially anhydrous; thesludge will thereupon be converted into a cokey mass that may be removedfrom the drum by hydraulic or other conventional decoking means. Alarger amount of anhydrous hydrogen chloride may be recovered by the useof sulfuric acid and the resulting sulfuric acid sludge may be chargedto a conventional sludge coker system for the recovery of sulfuric acid.Spent sulfuric acid from an alkylation system is an excellent medium forthis hydrogen chloride recovery step.

Instead of employing relatively pure hydrogen from source 42 I mayobtain hydrogen from renery gases which are rich in hydrogen. Such gasesmay be introduced through line ||2 to absorber ||3 which may operate atabout 100 F. under a pressure of about 900 pounds per square inch.Absorber oil may be butane from line 20 and line H4. Such oil may beintroduced by pump ||5 through line ||6 to the upper part of theabsorber tower for picking up the methane,

ethane, ethylene, propane, propylene, etc. in .the refinery gases. Theunabsorbed hydrogen will pass loverhead through line llllto be picked upby compressor 13. The rich absorber oil will pass through line H8 and.pressure reducing valve l i8 to receiver |20.from which the hydrocarbongases may be ventedA to fuel linesor 'other parts of the reiinerythrough line l 2! and the denuded oil may be returned by line |22, pumpH5 `and line lifi `back to `the top of the absorber.

The plant hereinabove described lis designed .to produce approximately98 volume percent yields of butane-free highoctane number iscmate. Acomparison of a charging stock Withithe resul-ting isomate issubstantially as follows:

vIf the heavier componentsV ofthe isomate are removed therefrom by.fractionation the remainder will have a clear A. S. T. M. octane numberwithin the approximate range of 85 to 9U. Withl cc. of tetraethyl leadper gallon this more volatile isomate will have .an octane number ofabout 19.5 to 100 and with 3 cc. of tetraethyl lead per gallon this morevolatile fraction may have an octane number as highas 105 to 110.

While I have describedin detail a speciiic embodiment of my invention itshould be under- .stood that the invention is notlimited to theapparatus or operating conditions recited in connection with thisspecific example. It has already been indicated that warm settler 5| maybe .an integral part .of th-e reactor andV may constitute an upper ,partoi'thereactor. Steam jackets, electrical heating means or the like maybe employed for maintaining the desired temperature in the reactor andin the Warm settler. Instead of. introducing' make-up aluminum chlorideas a slurry I may pre-'form make-up catalyst complex and introduce thispre-formed complex into each reactor either with the incoming chargingstock or at a point in the reactor above the charging stock inlet. I mayrecycle hydrogen and hydrogen chloride directly from the top of eachreactor to the Vbase thereof and draw oli the liquid products'fromapoint in the reactor below the reactor top. The aluminum chloride maybe introduced into the system in solution with charging stock or butaneor with recycled isobutane instead of as a slurry. These are onlyexamples of the many modifications and alternative operations which maybe employed and other modifications and alternatives will be apparent tothose skilled in the art from the above detailed description.

A feature of my invention is the means for introducing the hydrogenchloride activator into the reaction system, for preventing build-up ofcondensible hydrocarbons, and for diminishing .hydrogen chloriderequirements. Tests have shown that ii; isdesirable to have hydrogenchloride present during the reaction to the extent of at least abouttoabout ISO-pounds per barrel of light naphtha charged. However,theamount of Ihydrogen chloride; 'which disappears either through actualconsumption during the reaction, loss in the wash tower, etc. is verylow and never exceeds about .0.'5 pound per barrel of stock charged, andis usually about 0.3 pound per barrel or less, so that a veryconsiderable portion of the original hydrogen chloride charged will befound in the off-gases from product recovery system.

My method of .recovering the hydrogen chloride has many advantages. Theoff-gases from the settlers andthe hydrogen chloride stripping towerwill contain not only hydrogen chloride, but varying amounts-of'gasessuch as hydrogen, methane, etc. which if allowed to recycle wit-h thehydrogen chloride gases directly to the reaction zone would soon buildup in volume to anl undelsirable extent. I have --discovered that bypassing all ofV these gases through an absorber in which the chargingstock is used as the absorber oil, the'hydrogen chloride'is recoveredalmost quantitatively `while the methane etc. is` eliminated from thesystem. By this procedure, lonly a very small amount of make-up hydrogenchloride need be added, thus decreasing the cost of operating `theprocess considerably. The process also proceeds more smoothly due notonly to the absence of. extraneous light-gasesbut also because the.hydrogen :chloride .isintroduced into the sys- .tem-.inasubstantiallyconstant stream, the compositionofwhich -canbe easily controlled.Moreover, 4nospecifal regulating equipment is .required in orderto getthezhydrogenchloride into solution in thegproperamounts. Absorber 2d isgenerallyquite cool-say-,at from50 to 125 F. at the tcp and about100to.2-00 F. at lthe bottom under .3, pressure ogf about200 to 250pounds per square inch.

Stripper yBZand-settler 56 may operate at pressures sufficiently high.to overcome the pressure drop in IineZQ-'leading to absorber 2d, and noadditional compressors will then be required to inthis is by way ofillustration and not by way of limitation, and that `I intend to belimited only as set forth in the appended claims. Various de- -tailssuch as valves, pumps, automatic control devices, etc. have *beenvomitted forthe sake of simplicity since thoseskilled in the art will be.fully conversant vwith :such expedients.

I claim:

1. In a hydrocarbon conversion process wherein an'alumin-umha'lidecatalyst is activated by a hydrogen'halidathe .methodof operation which comprises contacting a hydrocarbon charging stockwith .an valuminum halide `catalyst in the presence 'of a 'substantial.amount of ya hydrogen halide activator in aconversion zone, separatingundissolved gasesfinclu'ding hydrogen halide and lighter .gases fromreactiony products, stripping dissolved hydrogen-halide yand lightergases from the 'separated products, .introducing gases from theseparation and stripping steps into the base of an .absorptionzone,.scrubbing saidgases with at Ile-ast a portion of thecharging stockin said :absorption zone-under conditions of temperature andpress-urefor effecting solution of the hydrogen .halide while. leavingat least a ysubstantial amount .of the `lighter gases unabsorbed in`said lcharging stock', venting the lighter unabsorbed .gasesiffrom `thetop of said absorption rzone in or- .der toprevent :a build-upyof suchgases inthe conversion system,A and introducing charging stock togetherwith labsorbed hydrogen `halide afrsefisa from the base of theabsorption zone to the conversion zone l 2. The method of claim 1wherein the conversion zone is maintained at a pressure oi at leastabout 500 pounds per square inch, wherein said separation and strippingsteps are effected at a pressure below 300 pounds per square inch,wherein said absorption step is eiected at a pressure within theapproximate range of 50 to 300 pounds per square inch and wherein thecharging stock together with absorbed hydrogen halide from the base ofthe absorption zone is pumped to reaction pressure and then passedthrough a heating zone before it is introduced into said conversionzone.

3. The method of claim 1 wherein the striprange by means of Van aluminumchloride cata-` lyst activated by hydrogen chloride in the presence ofhydrogen, the method of operation which comprises maintaining arelatively large body of aluminum chloride catalyst in a cenversionzone, introducing hydrogen, hydrogen halide and a charging stockcontaining substantial amounts of paralinic hydrocarbons of the butaneto hexane boiling range into said conversion zone, withdrawing productsand gases from the top of said conversion Zone to a separation zone,separating undissolved hydrogen chloride and lighter gases from saidproducts under conditions of temperature and pressure to prevent theremoval of any substantial amount of propane from the liquid products,stripping the liquid products under conditi-ons of temperature andpressure to eect removal of dissolved hydrogen chloride and lightergases without the removal of any substantial amount of propane orheavier hydrocarbons, introducing the gases from the separation andstripping steps into the base of an absorption Zone, countercurrentlycontacting said gases with at least a substantial portion of incomingcharging stock in said absorption Zone under conditions of temperatureand pressure for effecting solution of the hydrogen chloride in saidcharging stock while leaving at least a substantial amount of thelighter gases unabsorbed, Venting the lighter unabsorbed gases from thetop of said absorption zone and introducing charging stock together withdissolved hydrogen chloride from the base of said absorption zone intosaid conversion zone.

5. The method of claim 4 wherein the conversion zone is at a pressure ofat least 500 pounds per square inch, wherein the stripping zone isoperated at a pressure below about 300 pounds per square inch, whereinthe absorption zone is operated at a temperature within the approximaterange of 50 to 150 F. and at a pressure within the approximate range of50 to 300 pounds per square inch and wherein the charging stock anddissolved hydrogen chloride from the base of the absorption zone ispumped to conversion pressure and then heated to conversion temperaturebefore it is introduced into said conversion zone.

6. A method for the conversion of paraiiinic hydrocarbons of the butaneto hexane boiling range which method comprises introducing at least themajor portion of a charging stock which consists essentially of suchparatlnic hydrocarbons at the top of an absorption zone at a temperaturewithin the approximate range of 50 to 150 F. and a pressure within theapproximate range of 200 to 250 pounds per square inch, introducinghydrogen chloride containing gases at the base of said absorption Zone,removing undissolved gases from the top of said absorption zone, pumpingthe charging stock-hydrogen chloride solution from the base of theabsorption zone to a pressure within the approximate range of 800 to1000 pounds per square inch, heating said solution to a temperaturewithin the approximate range of 200 to 350 F. and introducing saidsolution into a conversion Zone containing a large emount of aluminumchloride catalyst material, introducing hydrogen into said conversionzone in amounts within the approximate range of to 300 cubic feet perbarrel of stock charged, contacting charging stock in said conversionzone with said aluminum chloride catalyst material at a space velocityof about .2 to 4 Volumes of charging stock per hour per volume ofaluminum chloride catalyst material in the conversion zone, removingproducts and gases from the top of said conversion zone to a separationZone maintained at a temperature within the approximate range of 50 to150 F.4 and a pressure within the approximate range of.200 to 250 poundsper square inch, separating undissolved hydrogen chloride and lightergases from liquid products in said separation zone, passing liquids fromsaid separation zone to a stripping zone operated under a pressurewithin the approximate range o 200 to, 250 pounds per square inch andwithra top temperature within the approximate range of 100 to 150 F. anda bottom temperature within the range oi-300 to 400V F., returningVhydrogen chloride and lighter gases from said stripping zone and fromsaid separation zone to the base of said absorber and introducingfurther amounts of hydrogen chlroide into said absorption zone invamounts suicient to effect the solution of an amount of hydrogenchloride within the approximate range of 3% to 10% by weight based ontotal stock charged to the conversion zone.

7. In a process wherein paraiin hydrocarbons containing atleast fourcarbon atoms per molecule are isomerized by passage in admixture withhydrogenchloride under isomerization conditions to a reaction zonecontaining an aluminum chloride isomerization catalyst, and a hydrogenchloride gas contaminated with other gases is .separated from theVreaction product in a stripping zone, the combination of steps whichcomprises introducing said contaminated 'hydrogen chloride from saidstripping zone to the base of' an absorption zone, `introducing atAleast a part of said paramn hydrocarbons at the upper part of saidabsorption zone, maintaining said absorption zone undersullcientpressure to elect sub.- stantial solution' of hydrogen chloridein thehydrocarbons therein while leaving at leasta substantial portion of thecontaminating gases undissolved, venting the undissolved contaminating`gases from the top of said absorption zone and introducing the solutionof hydrogen chloride in said hydrocarbons vfrom .the base of saidabsorption zone Ainto said reaction zone.

8. In a process wherein paraffin hydrocarbons containing at least fourVcarbon atoms Vper molecule are isomerized by passage in admixture withhydrogeny chloride under isomerization conditions to a reaction zonevcontaining'an aluminum chloride' isomerization catalyst,and a hydrogenchloride gas contaminated with other gases is separated from thereaction product, the combination of steps which comprises introducingsaid contaminated hydrogen chloride to the base of an absorption zone,introducing at least a part of said parafn hydrocarbons at the upperpart of said absorption zone, maintaining said absorption zone undersucient pressure to effect substantial solution of hydrogen chloride inthe hydrocarbons therein while leaving at least a substantial portion ofthe contaminating gases undissolved, venting the undissolvedcontaminating gases from the top of said absorption zone and introducingthe solution of hydrogen chloride in said hydrocarbons from the base ofsaid absorption zone into said reaction zone.

9. In a process wherein paraflin hydrocarbons containing at least fourcarbon atoms per molecule are isomerized by passage in admixture withhydrogen chloride under isomerizing conditions through a reaction zonecontaining an isomerization catalyst, activatable by hydrogen chloride,and Xed gases containin-g hydrogen and hydrogen chloride are separatedfrom the reaction products, the steps which comprise bringing said xedgases into intimate contact with at least a portion of the hydrocarbonfeed to said reaction zone ahead of said reaction Zone, under conditionseffecting solution of hydrogen chloride in said hydrocarbon feed whileleaving a substantial portion of the Xed gases other than hydrogenchloride undissolved, separating said hydrocarbon feed containing thehydrogen chloride from the undissolved portion of said fixed gases andthen passing the hydrocarbon feed containing hydrogen chloride to thereaction zone.

10. A process according to claim 9 in which the isomerization catalystis aluminum chloride.

11. In a process wherein parainic hydrocarbons containing atleast 4carbon atoms per molecule are isomerized by passage in admixture withhydrogen chloride under isomerization conditions to a reaction zonecontaining an aluminum chloride catalyst, and a hydrogen chloride gascontaminated with other gases is separated from the reaction product,the combination of steps which comprises introducing said contaminatedhydrogen chloride to the base of an absorption zone, introducing atleast a part of said parain hydrocarbons at the upper part of saidabsorption zone, maintaining said absorption zone under conditions oftemperature and pressure to effect substantial solution of hydrogenchloride in the hydrocarbons therein while leaving at least asubstantial portion of the contaminating gases undissolved, Venting theundissolved contaminating gases from the top of said absorption Zone andintroducing the solution of hydrogen chloride in said hydrocarbons fromthe base of said absorption zone through a heating Zone and thence tosaid reaction zone.

12. In a process wherein paraiiin hydrocarbons containing at least 4carbon atoms per molecule are isomerized by passage in admixture withhydrogen chloride under isomerization conditions through a reactionzonecontaining an aluminum chloride isomerization catalyst, the combinationof steps which comprises separating from the reaction product a hydrogenchloride gas contaminated with other gases, effecting said separation ata pressure which is not higher than reactor pressure so that there is nopressure increase between the reaction step and the separation step,introducing the separated hydrogen chloride and contaminating gases tothe base of an absorption Zone at a pressure not higher than thepressure in the separation step so that there is no pressure increasebetween the separation step and the absorption zone, introducing atleast a part of said paraffin hydrocarbons at an upper part of saidabsorption zone, maintaining said absorption zone under conditions oftemperature and pressure for effecting substantial solution of hydrogenchloride in the hydrocarbons therein while leaving at least asubstantial portion of the contaminating gases undissolved, venting theundissolved contaminating gases from th-e top of the absorption zone andpumping the solution of hydrogen chloride in said hydrocarbons from thebase of said absorption zone to said reaction zone.

JOSEPH K. ROBERTS.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date 2,100,354 Pier et al. Nov. 30,1937 2,220,091 Evering et al Nov. 5, 1940 2,220,092 Evering et al Nov.5, 1940 2,300,249 Evering et al Oct. 27, 1942 2,301,615 Chenicek et alNov. 10, 1942 2,310,523 Groll et a1. Feb. 9, 1943

